You do not have to get rid of Excel

"So Excel goes out then?" That is almost always the first question, and the answer is no. Not straight away, and often not entirely, ever. The switches that go wrong rarely go wrong on the software. They go wrong on the date when everything had to change at once.

Source or report, not both

The only thing that really has to change is which place is right. Right now that is the sheet: if the system and the sheet disagree, everyone believes the sheet. After the switch the system is the source and Excel is the report. That same sheet can keep existing, it just fills itself.

That is not a concession, that is the point. Excel is still the best tool there is for running a quick calculation, building a scenario or sending a list to your accountant. What you want to retire is the sheet as an administration, not as a calculator.

The order that does work

• Both run side by side. The system is live, so is the sheet, and one process goes over first.
• After a few weeks the sheet goes read-only. It is still there, you can open it, nothing in it can be changed.
• Whatever nobody opens goes to the archive. Usually it turns out half the tabs had been dead for months.

That second step matters most and gets skipped most often. As long as people can work in two places, they will, and then you have your old problem plus a new system. Read-only is not a punishment for your team, it is the only way to stop the numbers from drifting apart.

Nobody has to migrate over a weekend. If they do, the planning is wrong, not your team.

And when the sheet really cannot go

Sometimes there is a file in the chain that is not yours. The sheet your biggest client expects every Monday, the format your supplier sends its price list in, the file your accountant has wanted that way for ten years. You do not replace those, you generate them. An export in exactly that format, or an integration so the sheet updates itself.

The same reasoning goes for reporting. If someone in the office wants to keep making their own pivot tables, fine. As long as the data comes from the system instead of from a copy of a copy, nothing is wrong. Want those figures on a screen directly instead, that is a dashboard.

What this means for your planning

That you do not have to wait until everything is finished. The first process can go live while the rest still sits in the sheet, and that is the cheapest way to find out whether what you had in mind actually holds. If something turns out to need changing, at that point it is still an adjustment and not a rebuild.

What a phased switch looks like, from sheet to data model to a running system, is on from spreadsheets to software. What the migration itself involves is in migrating your Excel data.